Add more logging to cc scheduler to debug RAF frame loss.

BUG=393331
TEST=bots
R=brianderson@chromium.org

Review URL: https://codereview.chromium.org/533973002

Cr-Commit-Position: refs/heads/master@{#293046}

cc/scheduler/scheduler.cc

@@ -632,6 +632,9 @@ void Scheduler::ProcessScheduledActions() {
                  "SchedulerStateMachine",
                  "state",
                  AsValue());
+    VLOG(2) << "Scheduler::ProcessScheduledActions: "
+            << SchedulerStateMachine::ActionToString(action) << " "
+            << state_machine_.GetStatesForDebugging();
     state_machine_.UpdateState(action);
     base::AutoReset<SchedulerStateMachine::Action>
         mark_inside_action(&inside_action_, action);
@@ -642,8 +645,6 @@ void Scheduler::ProcessScheduledActions() {
         client_->ScheduledActionAnimate();
         break;
       case SchedulerStateMachine::ACTION_SEND_BEGIN_MAIN_FRAME:
-        VLOG(2) << "Scheduler::ProcessScheduledActions: "
-                   "ACTION_SEND_BEGIN_MAIN_FRAME";
         client_->ScheduledActionSendBeginMainFrame();
         break;
       case SchedulerStateMachine::ACTION_COMMIT:

cc/scheduler/scheduler_state_machine.cc

@@ -1086,4 +1086,17 @@ bool SchedulerStateMachine::HasInitializedOutputSurface() const {
   return false;
 }
 
+std::string SchedulerStateMachine::GetStatesForDebugging() const {
+  return base::StringPrintf("%c %d %d %d %c %c %c %d %d",
+      needs_commit_ ? 'T' : 'F',
+      static_cast<int>(output_surface_state_),
+      static_cast<int>(begin_impl_frame_state_),
+      static_cast<int>(commit_state_),
+      has_pending_tree_ ? 'T' : 'F',
+      pending_tree_is_ready_for_activation_ ? 'T' : 'F',
+      active_tree_needs_first_draw_ ? 'T' : 'F',
+      max_pending_swaps_,
+      pending_swaps_);
+}
+
 }  // namespace cc

cc/scheduler/scheduler_state_machine.h

@@ -237,6 +237,10 @@ class CC_EXPORT SchedulerStateMachine {
 
   bool CouldSendBeginMainFrame() const;
 
+  // TODO(zmo): This is temporary for debugging crbug.com/393331.
+  // We should remove it afterwards.
+  std::string GetStatesForDebugging() const;
+
  protected:
   bool BeginFrameNeededToAnimateOrDraw() const;
   bool ProactiveBeginFrameWanted() const;